package org.yagnus.langutils;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.lang.reflect.Modifier;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;
import java.util.regex.Pattern;

public class Reflections {

    public static Collection<String> getClasses(String pkgnm, String regexp) {
        Set<String> allClasses = new HashSet<String>();
        allClasses.addAll(getJarClasses(regexp));
        allClasses.addAll(getResourseClasses(pkgnm));
        return allClasses;
    }

    public static <T> Collection<Class<T>> getClasses(String pkgnm,
            String regexp, Class<T> superInterface) {
        return getClasses(pkgnm, regexp, superInterface, true);
    }

    /**
     * all super interfaces are exhausted or if a match is found. This methods
     * recursively climes ancestor list and interface tree until
     * 
     * @param <T>
     * @param pkgnm
     * @param superInterface
     * @param skipAbstract
     * @return
     */
    public static <T> Collection<Class<T>> getClasses(String pkgnm,
            String regexp, Class<T> superInterface, boolean skipAbstract) {

        ClassLoader classLoader = Thread.currentThread()
                .getContextClassLoader();
        if (classLoader == null)
            return Collections.emptyList();

        ArrayList<Class<T>> ret = new ArrayList<Class<T>>();

        Collection<String> classNames = getClasses(pkgnm, regexp);
        // System.out.println("Going to check " + classNames.size());
        for (String cn : classNames) {
            if (cn == null)
                continue;
            Class<?> c;
            // System.out.println("Checking " + cn);
            try {
                c = classLoader.loadClass(cn);
            } catch (ClassNotFoundException e) {
                continue;
            }
            if (c == null)
                continue;
            // System.out.println("\thave class" + cn);
            // getInterfaces gets only declared interfaces, not all available
            // interfaces, so have to iterate upward.
            LinkedList<Class> ifs = new LinkedList<Class>();
            for (Class<?> t : c.getInterfaces())
                if (t != null)
                    ifs.add(t);
            ifs.add(c.getSuperclass());

            while (!ifs.isEmpty()) {
                Class<?> t = ifs.poll();
                if (t != null) {
                    // System.out.println("\thave class" + cn +
                    // " Checking interface "+ t.getName());
                    if (t == superInterface
                            && (!skipAbstract || !Modifier.isAbstract(c
                                    .getModifiers()))) {
                        ret.add((Class<T>) c);
                        break;
                    }
                    for (Class<?> t2 : t.getInterfaces())
                        ifs.add(t2);
                    ifs.add(t.getSuperclass());
                }
            }
        }

        return ret;
    }

    /**
     * Also copied from some website when searching for how to find classes
     * inside a package
     */
    public static Collection<String> getJarClasses(String regexp) {
        return getJarClasses(Pattern.compile(regexp));
    }

    public static Collection<String> getJarClasses(Pattern regexp) {
        ArrayList<String> ret = new ArrayList<String>();

        for (String clss : getJarClasses()) {
            if (regexp.matcher(clss).matches())
                ret.add(clss);
        }

        return ret;
    }

    public static Collection<String> getJarClasses() {

        ArrayList<String> ret = new ArrayList<String>();

        ClassLoader cl = ClassLoader.getSystemClassLoader();
        for (String cp : System.getProperty("java.class.path").split(
                System.getProperty("path.separator"))) {

            File jar = new File(cp);
            if (cp.endsWith(".jar")) {
                // System.out.println("Checking " + cp);
                JarInputStream is;
                try {
                    is = new JarInputStream(new FileInputStream(jar));
                } catch (FileNotFoundException e) {
                    continue;
                } catch (IOException e) {
                    continue;
                }
                // System.out.println("Checking " + cp + " opened fine.");

                // new FileInputStream(jar));
                JarEntry entry;
                do {
                    try {
                        entry = is.getNextJarEntry();
                    } catch (IOException e) {
                        break;
                    }
                    if (entry != null) {
                        // System.out.println("Entry is " + entry.getName());
                        if (entry.getName().endsWith(".class")
                                && entry.getName().indexOf("$") < 0) {
                            // ret.add(Class.forName(entry.getName()));
                            String cn = entry.getName();
                            cn = cn.substring(0, cn.length() - 6);
                            cn = cn.replace('/', '.');
                            ret.add(cn);
                        }
                    }
                } while (entry != null);
            }
        }
        // System.out.println("Returning size " + ret.size());
        return ret;

    }

    /**
     * Originally copy and pasted from snippets.dzone.com
     */
    public static Collection<String> getResourseClasses(String packageName) {
        ClassLoader classLoader = Thread.currentThread()
                .getContextClassLoader();
        if (classLoader == null)
            return Collections.emptyList();

        String path = packageName.replace('.', '/');

        Enumeration<URL> resources;
        try {
            resources = classLoader.getResources(path);
        } catch (IOException e) {
            return Collections.emptyList();
        }
        List<File> dirs = new ArrayList<File>();
        while (resources.hasMoreElements()) {
            URL resource = resources.nextElement();
            dirs.add(new File(resource.getFile()));
        }
        ArrayList<String> classes = new ArrayList<String>();
        for (File directory : dirs) {
            classes.addAll(findResourceClasses(directory, packageName, 100));
        }
        return classes;
    }

    private static List<String> findResourceClasses(File directory,
            String packageName, int depthLimit) {
        if (depthLimit <= 0)
            return Collections.emptyList();

        List<String> classes = new ArrayList<String>();
        if (!directory.exists()) {
            return classes;
        }
        File[] files = directory.listFiles();
        for (File file : files) {
            if (file.isDirectory()) {
                assert !file.getName().contains(".");
                classes.addAll(findResourceClasses(file, packageName + "."
                        + file.getName(), depthLimit - 1));
            } else if (file.getName().endsWith(".class")
                    && file.getName().indexOf('$') < 0) {
                classes.add(packageName
                        + '.'
                        + file.getName().substring(0,
                                file.getName().length() - 6));
            }
        }
        return classes;
    }

}
